Andrew Gross January 20, 2021
The headlines and articles screamed about the latest study that purports to show that infant circumcision causes harm. “Undergoing circumcision as an infant has delayed psychological complications.”  “Neonatal circumcision has delayed psychological implications as an adult: Study.” 
In fact the researchers who wrote the study published in the journal Heliyon  did not make those claims. They cautiously concluded that their findings suggest that early infant circumcision might have an impact on adult traits and behaviors.
In this article I’ll analyze the strengths, weaknesses, and limitations of the study.
Results and Strengths The study involved 211 uncircumcised men and 408 men circumcised as infants. The authors found that the circumcised men reported higher levels of avoidance and anxiety, perceived stress, and emotional instability than the uncircumcised men. However there was no significant difference between the two groups in terms of empathy and trust. The researchers admitted, “The psychological differences that we found ... are not sufficiently severe in themselves to be suggestive of pathology.”
Study participants were limited to uncircumcised men and men circumcised within one month of birth. The method of recruitment was a neutral platform, and the survey title did not mention circumcision, reducing the likelihood that selection bias was a factor. By limiting participation to American men, the likelihood of cultural bias and demographic variables was reduced. I commend the authors for these study strengths.
Weaknesses and Limitations
The first evident weakness is that results were based on participant self-reports, a limitation that the authors acknowledged “might have hindered participants from answering honestly.” One should be wary of circumcision studies based on self-identification, which can be unreliable. A 2002 study of 1,508 adolescent boys found that 23% of circumcised males and 31% of uncircumcised males didn't know their status. For those subjects who didn't know - even after viewing images of a circumcised penis and an uncircumcised penis - just 82% of the circumcised males and 43% of the uncircumcised males were able to correctly identify their status. 
While the introduction included citations to several studies on short-term and long-term effects of pain, the study did not explore the possible effect of pain relief during the procedure on adult behaviors and traits. This is a significant weakness. The average age of the circumcised participants was 36, meaning participants were circumcised during the 1970s and 1980s - long before pain relief became a standard part of the newborn circumcision procedure. A study conducted in 1998 found that just 45% of responding physicians provided pain relief during the procedure.  Yet a University of Rochester study found that by 2003, 97% of residency programs trained physicians to use a local or topical anesthetic.  The dramatic change may be due in part to changing policy statements of the American Academy of Pediatrics. By 1999 the AAP recommended (and reiterated in 2012) that all patients should be given adequate pain relief to help them manage the pain.   The participants in the present study who did not receive pain relief were circumcised without the standard of care recommended by the AAP and currently practiced.
The study did not measure participants' attitudes towards circumcision or their circumcision status. A Queen’s University study found that a man’s attitude toward his circumcision status affected body image and sexual functioning.  Many angry circumcised men have reported obsessive and destructive traits and behaviors based on their feelings about their circumcision status.  The authors did not appear to consider the possibility that attitudes toward circumcision may play a greater role than the procedure itself. 
The authors admitted that “sociodemographic data such as religious affiliation and socioeconomic status ... could have played a role in parent-infant relations hence affecting attachment development.” They also acknowledged that the population base from which the participants came “tend to be younger and more educated, but report lower incomes and higher unemployment” than the general population.
Conflicts of Interest
It is striking that the authors declared no conflicts of interest. Brian Earp has written dozens of papers and articles critical of circumcision.  He has been a keynote speaker at anti-circumcision conferences, and a 2016 symposium honored him with the "Jonathon Conte Award - for furthering the cause of genital autonomy."  Authors Astrid Højgaard and Jørgen Hoppe submitted written statements in 2014 in which they advocated that Danish authorities should prohibit elective circumcision of infant boys.  
Author Michael Winterdahl proudly declared the purpose of the study. “We wanted to challenge the assumption that there are no delayed consequences of infant circumcision apart from the purely physical...”  Winterdahl expressed his desire that parents would use the findings when they make a decision about circumcision.
While researcher bias doesn’t automatically discredit a study, readers should be particularly skeptical when considering a paper in which data, analysis, and conclusions support the researchers’ partisan agenda. The authors may not consider their history of hostility to circumcision nor their stated mission to criminalize circumcision of minor boys relevant. But readers have a right to know the authors’ personal interests when assessing the validity of the study.
While taking steps to avoid self-selection bias, the Heliyon study suffers from several limitations. A study that explores the effect of pain relief, includes participants' attitudes toward circumcision, and avoids self-reporting would provide a measurement of the possible effect of infant circumcision on adult male behaviors that might be more worthy of public confidence and trust.
Furthermore, researchers should be open and honest about their own biases and agendas. Ideally a researcher would conduct a study in order to gain information and insight - not to advance an agenda. Regrettably, that is not the case with the present study. I would suggest that many flaws and limitations could be avoided if researchers with competing agendas would work with - rather than against each other.
 Aarhus University News Release; “Infant circumcision may lead to social challenges as an adult”; EurekAlert; December 17, 2020
 Hina Zahid; “Neonatal circumcision has delayed psychological implications as an adult: Study”; Medical Dialogues; December 18, 2020
 Michael Winterdahl et al; “Neonatal circumcision is associated with altered adult socio-affective processing”; Heliyon; November 26, 2020
 Risser, et al; “Self-Assessment of Circumcision Status by Adolescents”; American Journal of Epidemiology; 2004
 H J Stang; "Circumcision practice patterns in the United States; Pediatrics; June 1998
 Daniel Yawman M.D. et al; “Pain Relief for Neonatal Circumcision: A Follow-up of Residential Training Practices”; Pediatric Education; July 1, 2006
 Carole M. Lannon, MD et al; "Circumcision Policy Statement"; Pediatrics; March 1, 1999
 Susan Blank M.D. et al; "Task Force on Circumcision Policy Statement"; Pediatrics; September 2012
 Jennifer A. Bossio et al; “Attitude Toward One’s Circumcision Status Is More Important than Actual Circumcision Status for Men’s Body Image and Sexual Functioning”; Archives of Sexual Behavior; September 11, 2017
 “Intactivism is a Mental Disorder”; Circumcision Choice; May 8, 2019
 Author Brian Earp has argued that false beliefs about circumcision are associated with satisfaction about one’s circumcision status. Brian D. Earp et al; "False beliefs predict increased circumcision satisfaction in a sample of US American men"; Culture, Health & Sexuality; July 2018. However there are several flaws with the study he conducted. Stephen Moreton; "Do False Beliefs Predict Increased Circumcision Satisfaction in Men?"; Advances in Sexual Medicine; April 17, 2020. Andrew Gross; “Do happily circumcised men have false beliefs?”; Circumcision Choice; February 2020
 Brian D. Earp; "Curriculum Vitae"; University of Oxford
 Hugh Young; Facebook post; September 16, 2016
 Astrid Højgaard; email to Ivar Gøthgen; January 20, 2014. “Det bør ikke være tilladt at udføre ikke-indicerede indgreb på drengebørns penis.” Translation: “It should not be allowed to perform unspecified interventions on the penis of boys.” (landing page)
 Jørgen Hoppe; email to Ivar Gøthgen; January 20, 2014. "Da barnet kun kan smertedækkes helt når det lægges i fuld narkose og først kan lægges i fuld narkose når det er 1 år gammelt, er det uacceptabelt,at vejledningen tænkes at anbefale omskæring i de første uger af barnets levetid." Translation: "As the child can only be completely covered in pain when he is placed under general anesthesia and can only be placed under full anesthesia when he is 1 year old, it is unacceptable that the guide is intended to recommend circumcision in the first weeks of life of the child." (landing page)